Ring laser angular rate sensors are well known and exemplified by U.S. Pat. Nos. 3,323,411 and 3,373,650 issued to Killpatrick, which are incorporated herein by reference thereto. Present day ring laser angular rate sensors generally include a thermally and mechanically stable laser block having a plurality of formed cavities for enclosing a gas. Mirrors are placed at the extremeties of the cavities for reflecting laser beams and providing an optical close-loop path.
Associated with such sensors in a phenomenon called lock-in which has been recognized for some time in the prior art and has been solved by rotationally oscillating the sensor (dither). The means for accomplishing the dither conventionally includes a piezoelectric actuator connected to a suspension system which causes the block of the sensor to oscillate angularly at the natural mechanical resonant frequency of the suspension system. The dither motion is superimposed upon the actual rotation of the sensor in inertial space. The prior art includes various approaches to recover inertial rotation data free from dither and this is not form part of the present invention.
Dither suspension mechanisms in the prior art include those shown, by way of example, in U.S. Pat. Nos. 4,312,557 issued to McNair, 4,411,527 issued to Gamertsfelder et al, and 4,436,423 issued to Kumer et al.
Advances in the art of ring laser angular rate sensors have now made it possible to provide laser sensors having a laser block in the order of 1 inch square. Reduction of the size of the sensor has many advantages including lower cost and lower weight. Dither suspension systems of the prior art do not lend themselves well to small sensor blocks. This is so since the dither mechanism would have to be reduced in size, which generally causes the dither mechanism cost to increase. Further, many dither mechanisms require a large aperture in the laser block for receiving the dither mechanism, and securing the mechanism to the inner wall of the block created by the aperture.
In is an object of the present invention to provide a low cost dither suspension mechanism for ring laser angular rate sensors which is simple to build resulting in low cost.